1. Field of the Invention
The present invention relates to a method for forming a pattern onto an article during an injection molding thereof and an apparatus for the same, for preventing impressions of a heating board from remaining on the surface of the molded article or molding.
2. Description of the Related Art
Conventionally, as decorative patterning methods for three-dimensional solid moldings, a laminate method and a transfer printing method are known. In the laminate method, after a film on which a pattern has been printed is shaped or concurrently therewith, the film is adhered to a substrate, or while or after the film is shaped, the film is filled with a resin. On the other hand, in the transfer printing method, only a pattern ink of a film on which the pattern has been printed is transferred to a molded article or molding.
As a transfer printing method, a method disclosed in Japanese Patent Laid-Open Publication Serial No. SHO 62-196113, published on Aug. 29, 1987 is known. In this method, as will be described later, a heating board which sucks a pattern-bearing film thereon is moved into a space between a male mold and a female mold which are spaced apart from each other by a predetermined distance. Then the pattern-bearing film heated by the heating board is vacuum sucked to the inner surface of the female mold. Thereafter, the heating board is retreated to the outside of the space between the male mold and the female mold. Next, the male mold and the female mold are clamped or closed. In the cavity defined by these molds, a molten resin is injected to form a molded article. Thus, the pattern-bearing film is attached to the surface of the molded resin article.
In this method, however, when the pattern-bearing film is sucked to the heating board, air is caught between the heating board and the pattern-bearing film. This air remains as air bubbles so that the pattern-bearing film is not uniformly heated. In addition, marks or impressions of vacuum holes defined on the heating board remain on the surface of the final molding having the pattern-bearing film sucked thereby. Thus, the appearance of the molding is adversely affected.
To solve this problem, a method as disclosed in Japanese Patent Laid-Open Publication Serial No. HEI 5-301250 (i.e., Japanese Patent Application Serial No. HEI 4-108271) has been proposed. In this method, a square-shaped holding flame is protruded from a peripheral edge of the hating surface of the heating board so as to contact with the pattern-bearing film, and a concave portion is formed at the inside of the annular holding frame. When the pattern-bearing film is located to be opposed to the heating board in order to heat the film, the concave portion prevents the film from direct contact with the heating surface of the heating board. Thus, the concave portion restrains the marks or impressions of vacuum holes from being formed on the surface of the final molding so that the appearance of the molding is fortunately affected.
The present invention is made from the above-mentioned point of view. A first object of the present invention is to provide a method for forming a pattern onto an article during an injection molding thereof and an apparatus for the same, in which the pattern-bearing film can be transferred to a position opposed to the internal surface of the female mold under the condition that the slacks or wrinkles are not formed on the film, so that the pattern-bearing film can be accurately positioned to the internal surface of the female mold.
A second object of the present invention is to provide an apparatus for forming a pattern onto an article during an injection molding thereof and an apparatus for the same, in which the heating board can be simply and securely pressed into the female mold.
A third object of the present invention is to provide an apparatus for forming a pattern onto an article during an injection molding thereof and an apparatus for the same, in which the heating board can be securely pressed into the parting surface of the female mold.
A fourth object of the present invention is to provide an apparatus for forming a pattern onto an article during an injection molding thereof and an apparatus for the same, in which the heating board can uniformly heat the entire pattern-bearing film.
A fifth object of the present invention is to provide an apparatus for forming a pattern onto an article during an injection molding thereof and an apparatus for the same, in which a insulation board waiting at a standby position can prevent the pattern-bearing film or the like from being heated and deformed-in the standby position.
A sixth object of the present invention is to provide an apparatus for forming a pattern onto an article during an injection molding thereof and an apparatus for the same, in which the pattern-bearing film can be cut by a simple structure and the cutting is low in cost.
According to one aspect of the present invention, the first object is accomplished by a method for forming a pattern onto an article during an injection molding thereof, comprising the steps of: feeding a pattern-bearing film to a molding position where a male mold and a female mold are opposed; heating said pattern-bearing film by a heating board so as to soften it, said heating board having a heating surface and being movable into and away from a space between said male mold and said female mold; transferring said pattern-bearing film to an internal surface of said female mold so as to contact said pattern-bearing film with said internal surface; causing said male mold and said female mold with said pattern-bearing film therein to approach each other to form a closed molding cavity; and injecting a molten resin into said cavity to form a molded article to adhere said pattern-bearing film to the surface of said article, wherein the improvement comprises the step of: feeding the pattern-bearing film from a film supplying section to a position which is opposed to the internal surface of the female mold; fixing a distal end of the pattern-bearing film by a film fixing frame arranged at a downstream-side of the female mold along the film feeding direction; retreating the pattern-bearing film to the film supplying section so as to tighten up the pattern-bearing film; and fixing the pattern-bearing film on the parting surface of the female mold, whereby the heating board is moved into a position where the heating surface thereof is opposed to the pattern-bearing film fixed on the parting surface, and then the pattern-bearing film is softened by the heating surface of the heating board means.
In the method, after the pattern-bearing film is fed to the female mold, the distal end of the film is fixed under a lower portion of the female mold, and at the same time the film is retreated by a tensile force from the film supply portion. Thus, this tightens up the film so that the slacks or wrinkles cannot be formed on the film. Therefore, the film can be fortunately spread around the parting surface of the female mold.
According to another aspect of the present invention, the second object is accomplished by an apparatus for forming a pattern onto an article during an injection molding thereof, comprising: means for feeding a pattern-bearing film to a molding position where a male mold and a female mold are opposed; heating board means for heating said pattern-bearing film so as to soften it, said heating board means having a heating surface and being movable into and away from a space between said male mold and said female mold; means for transferring said pattern-bearing film to an internal surface of said female mold so as to contact said pattern-bearing film with said internal surface; means for causing said male mold and said female mold with said pattern-bearing film therein to approach each other to form a closed molding cavity;.and resin injecting means for injecting a molten resin into said cavity to form a molded article to adhere said pattern-bearing film to the surface of said article wherein the improvement comprises: a film suppressing frame for fixing said peripheral portion of said pattern-bearing film which has fed by said feed means; fitting groove means, defined on the periphery of a parting surface of said female mold, for holding the film suppressing frame; and a sliding rod, slidably supported within a through-hole formed in the female mold and extended through the parting surface-thereof, for moving the film suppressing frame so that the film suppressing frame is-pressed into the fitting groove means with the pattern-bearing film interposed therebetween, whereby the heating board is moved into a position where the heating surface thereof is opposed to the pattern-bearing film fixed on the parting surface, and then the pattern-bearing film is softened by the heating surface of the heating board means.
In the apparatus, the film suppressing frame is pressed to the female mold through the sliding rod arranged in the female mold, in such a manner that the female mold embraces the frame. Thus, the pressing of the frame is performed by a simple structure, and the film is accurately positioned to the internal surface of the female mold. Also, the film suppressing frame is constituted to advance from and retreat to the female mold. Thus, this causes a space between the both molds and an outside standby position to be useless. A space around the apparatus can be effectively utilized.
According to the other aspect of the present invention, the third object is accomplished by an apparatus for forming a pattern onto an article during an injection molding thereof, wherein the improvement comprises: a pair of holding members, arranged on both sides of the female mold, for holding the heating board means so as to be opposed to the parting surface of the female mold, the holding members being movable along a direction connecting the male and female molds so as to press the heating board means to the female mold.
In the apparatus, the heating board is held or surrounded by the holding members provided on the female mold, in such a manner that the female mold embraces the heating board. Thus, the heating board is intensely. pressed to the female mold. Even if the compressed air is blown from the heating board at the vacuum formation, the holding members prevent the heating board from being apart from or removed from the female mold. The driving device can be miniaturized, as compared that the heating board is pressed into the female mold by means of a driving device disposed extremely apart from the molds.
According to the other aspect of the present invention, the fourth object is accomplished by an apparatus for forming a pattern onto an article during an injection molding thereof, the improvement wherein said heating board means is divided into a plurality of blocks, and each block independently controlling the amount of the heat generated by the block.
In the apparatus, each block independently controlling the amount of the heat generated by the block. Thus, the temperature distribution can be uniform.
According to the other aspect of the present invention, the fifth object is accomplished by an apparatus for forming a pattern onto an article during an injection molding thereof, wherein the improvement comprises: insulation board means for covering the entire heating surface of the heating board means when the heating board means is waiting at a standby position defined apart from the space between the male and female molds.
In the apparatus, the insulation board prevents the heat radiated from the heating board from excessively heating the pattern-bearing film before forming, the forming apparatus and so forth, whereupon this restrains melting, deformation, fire and so forth of the pattern-bearing film.
According to the other aspect of the present invention, the sixth object is accomplished by an apparatus for forming a pattern onto an article during an injection molding thereof, wherein the improvement comprises: heating wire means, arranged at the upstream-side of the female mold along the film feeding direction, for heating the pattern-bearing film so as to cut it into a proceeding portion and a following portion thereof when the heating board means is pressed into the parting surface of the female mold.
In the apparatus, when the heating board is pressed into the parting surface of the female mold, the pattern-bearing film is automatically cut by the heating wire. In addition, it is simple in structure and is lower in cost.
Also, the pattern-bearing film opposed to the parting surface of the female mold may be heated by the heating board in a non-contact state. Alternatively, the pattern-bearing film opposed to the parting surface of the female mold may be heated by the heating board in a contact state.
These and other objects, features and advantages of the present invention will become more apparent in light of the following detailed description of best mode embodiments thereof, as illustrated in the accompanying drawings.